Power plants – Pressure fluid source and motor – Servo-motor having externally operated control valve sets...
Utility Patent
1998-08-12
2001-01-02
Lopez, F. Daniel (Department: 3745)
Power plants
Pressure fluid source and motor
Servo-motor having externally operated control valve sets...
Utility Patent
active
06167702
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a hydraulic controller, in particular for the control of the rotating mechanism of an excavator.
2. Discussion of the Prior Art
A hydraulic controller in accordance with the State-of-the-technology is disclosed e.g. in DE 44 05 472 A1. The hydraulic circuit diagram of this known hydraulic controller is, for better understanding of the invention, reproduced in
FIG. 2
of the drawings and will be briefly described below with reference to FIG.
2
.
The known rotating mechanism controller
1
, illustrated in
FIG. 2
, includes a drive hydraulic pump
2
which is connected via working lines
3
,
4
with a drive hydraulic motor (not shown) for the drive of the rotating mechanism (likewise not shown) of an excavator. The hydraulic controller includes a hand controller
5
which is in connection with a pre-control arrangement
8
via control lines
6
and
7
. By means of the pre-control arrangement
8
, the necessary setting pressure is delivered to an adjustment arrangement
9
, which setting pressure is obtained directly from the control pressure prevailing in the control lines
6
,
7
. The adjustment arrangement includes a setting piston
12
, arranged between two setting pressure chambers
10
and
11
, which setting piston acts upon the displacement volume of the working hydraulic pump
2
.
Upon return of the hand controller
5
into its neutral position, the pre-control arrangement
8
likewise takes up its neutral position, so that the adjustment arrangement
9
is no longer supplied with hydraulic energy, i.e. with setting pressure. The working hydraulic pump
2
is slowly swung back to zero displacement volume via the return springs
13
and
14
. Thereby, from an after-suction arrangement
74
, which consists of the check valves
15
and the after-suction filter
16
, pressure fluid is drawn into that setting pressure chamber
10
or
11
the volume of which increases in the return procedure.
This known rotating mechanism controller has, however, several grave disadvantages. Through the after-suction of pressure fluid out of the pressure fluid tank
17
, particles of dirt can penetrate into the hydraulic controller. This problem can be only partially removed even by means of the after-suction filter
16
. Since, during the after-suction procedure, only slight pressure differences prevail, the filter must be relatively large, which conflicts with the goal of a lesser constructional size of the hydraulic controller. Beyond this, the after-suction filter
16
must be regularly cleaned and serviced.
Insofar as particles of dirt penetrate into the pre-control arrangement
8
and lock this in one of its control positions, operational safety is put significantly at risk. The valve of the pre-control arrangement
8
is thereby not returned into its neutral position, but remains in one of its control positions. If, now, the respective other direction of rotation of the rotating mechanism is set by means of the hand controller
5
, i.e. the respective other control line
6
or
7
is acted upon with control pressure, this does not lead to the intended reversal of the swing-out direction and thus the delivery direction of the working hydraulic pump
2
. Rather, the working hydraulic pump
2
continues to deliver in its previously set delivery direction, so that the direction of rotation of the rotating mechanism is, contrary to the intentions of the user, not reversed, but the rotating mechanism is accelerated in the opposite direction. In practice, this can represent a significant source of danger.
A further disadvantage arises with the known rotating mechanism controller in that in control of the driving hydraulic pump it is not detected whether pressure fluid in sufficient quantity is available in the working lines
3
and
4
. In this respect, problems can arise in particular in that the feed filter
18
of the feed arrangement
19
is blocked and the feed pump
20
cannot feed pressure fluid in sufficient quantity into the working circuit
3
,
4
. Thus, there is a danger of damage to the drive hydraulic pump
2
and to the drive hydraulic motor (not shown).
SUMMARY OF THE INVENTION
It is thus the object of the present invention to so further develop the known hydraulic controller that operational problems e.g. due to the penetration of dirt particles or the blocking of filters are avoided.
The invention is based upon the insight that by obtaining the setting pressure for the adjustment arrangement from the feed pressure made available by the feed arrangement, two goals are simultaneously attained. On the one hand it is ensured that after return of the hand controller and thus also of the pre-control arrangement into their respective neutral positions, filtered pressure fluid, for balancing the volume differences during the return procedure flows into the setting pressure chambers of the adjustment arrangement. An after-suction arrangement can be omitted. On the other hand, it is ensured that in case of a failure of the feed arrangement, e.g. through blockage of the feed filter, no setting pressure is available and thus the working hydraulic pump swings back into its neutral position. Thus, damage to the working hydraulic pump and the working hydraulic motor is reliably avoided in the case of this fault.
The pre-control arrangement can be constituted in per se known manner as a 4/3-way valve. However, it is more advantageous, corresponding to claim
3
, to form the pre-control arrangement in a divided manner, with separate valve regions each respectively for one control pressure chamber of the adjustment arrangement. By these means, a separate control of the right and left slewing of the rotating mechanism is attained. Insofar as with this arrangement dirt particles might still penetrate into the valve of the pre-control arrangement and block this in one of its control position, it is ensured that upon change of the control direction by means of the hand controller and corresponding reversal of the pressure action on the control lines
6
and
7
no unintended acceleration of the rotating mechanism in the previously selected, opposite direction occurs. The pre-control arrangement can in this case be formed as a 6/3-way valve.
Corresponding to the invention, the pressure regulation valve provided between the feed arrangement and the pre-control arrangement, or—in the case of separate control of left and right slewing—the two pressure regulation valves provided, set the setting pressure to the control pressure prevailing in the control line or a slightly higher pressure. The pressure difference between the control pressure and the setting pressure can be attained by means of spring action on the pressure regulation valve or the pressure regulation valves.
Corresponding to the invention, a pressure cut-off valve may be provided between the control pressure lines and the pressure fluid tank, in order to limit the pressure in the control lines to a predetermined maximum pressure.
Further, corresponding to the invention, a brake valve may be provided, in order to make possible a slow, delayed breaking of the rotating mechanism.
REFERENCES:
patent: 4075841 (1978-02-01), Hamma et al.
patent: 4571940 (1986-02-01), Wuchenauer
patent: 4001 888 A1 (1990-08-01), None
patent: 44 05 472 A1 (1995-08-01), None
patent: 0 056 865 (1982-08-01), None
patent: 0 057 930 (1982-08-01), None
Brueninghaus Hydromatik GmbH
Lopez F. Daniel
Scully Scott Murphy & Presser
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